Sliding tray reactor

ABSTRACT

Hydrogen gas is generated on demand by reacting hydrochloric acid (haloacid) and a pure metal by flowing the acid upwardly through a bed of metal particles held on a distributor plate within a sliding tray. The tray reciprocates in a retaining vessel. A port in the retaining vessel can be aligned with a drain port in the sliding tray (below the distributor plate) so that the solution in the bed can be shunted directly to an annulus between the retaining vessel and the reactor jacket, thereby eliminating contact of acid and metal and stopping the generation of hydrogen. A coolant may be circulated in the base of the retaining vessel to control the temperature of the acid as it enters the bed, thereby helping to control the reaction rate. A hydrogen generator reactor includes one or more such sliding trays housed within a jacket.

The U.S. Government has rights in this invention pursuant to Contract No. F04704-82-C-0038.

TECHNICAL FIELD

The present invention relates to an improved apparatus and method for generating essentially pure hydrogen gas on demand by the reaction of an acid with pure metal particles in a controlled environment. Features of the reactor allow efficient and controllable operation to produce the gas with a minimum waste.

BACKGROUND ART

While it has long been known that hydrogen gas can be generated by the reaction of acids with pure metals, efficient reactors for the controlled production of essentially pure hydrogen gas on an "as needed" basis have not been pursued. For the deep basing environment of the Intercontinental Ballistic Missile program, however, there is incentive to optimize the method and apparatus for generating hydrogen. In the deep basing environment, a network of tunnels, drifts, and raises will be located far enough underground that the base could survive a very large scale nuclear attack. A power source that can operate without access to outside resources, particularly without the need for combustion air, large scale cooling, or significant waste or by-product disposal, is essential to the survival and post-attack usefulness of such a base. The optimized method and apparatus of the present invention for generating essentially pure hydrogen gas on a demand basis uses dilute hydrochloric acid or another suitable halide acid to provide a non-toxic waste product, including soluble metal chlorides (or halides), and hydrogen gas that is suitable for use in a hydrogen-halide fuel cell. Storage of hazardous hydrogen gas is minimized. The acid is a by-product of the fuel cell operation.

SUMMARY OF THE INVENTION

Essentially pure hydrogen gas can be generated in an efficient manner on demand by the reaction of hydrochloric acid with a metal. The hydrochloric acid solution is introduced to the bottom of a bed of essentially pure metal particles and is forced upwardly through the bed to promote the reaction. The flow of acid through the bed should be sufficiently low to avoid fluidizing the particles in the bed so that all the particles remain in the bed and dissolve completely. The flow is countergravity so that all the metal dissolves without blocking or clogging a distributor plate, which supports the bed. In this way a substantially pure hydrogen gas stream is generated using a minimum amount of pure metal. The output of hydrogen gas is maximized per unit volume of metal. The design allows metal to be added to each bed without interfering with the operation of the generator.

The generator usually has multiple stages, with the first stage having a bed of iron and a later stage, a bed of zinc. Zinc has a higher reaction rate with hydrochloric acid (by about 500 times) than the iron particles. Thus, as the acid is diluted by the reaction, the susceptance of the metal particles to the acid is increased to promote the reaction. Nearly all the HCl can be consumed.

The rate of reaction is controllable by cooling the incoming hydrochloric acid with a refrigerant, such as cooling water, that flows below the distributor plate.

Each processing stage of the generator preferably includes a retaining vessel and an internal sliding tray received within the retaining vessel. The refrigerant is introduced under the retaining vessel and creates a variable volume chamber between the bottom of the vessel and the bottom of the tray. By restricting the flow of refrigerant from the chamber, the tray can be raised or lowered above the bottom of the vessel. A pair of ports (one on the vessel and one on the tray) can be aligned to allow fluid within the tray to flow from the tray and the vessel, draining the bed quickly and stopping the generation of hydrogen.

The metal particles are deposited on a distributor plate mounted in the sliding tray above the bottom to define a cavity, and hydrochloric acid is forced upwardly from the cavity through the distributor plate and into the bed. The tray port generally communicates with the cavity and is on the tray wall below the distributor plate. HCl solution need not enter the bed when stopping the reaction is desired. In this way, manufacture of unwanted hydrogen gas is avoided. The need to flood the bed with a nonreactive, quenching solution to slow or stop the reaction is also eliminated. Hydrogen can be controllably generated on demand, and only a minimum of hydrogen need be stored.

Surges of acid solution between stages are controlled with a surge control means that includes no moving parts. A pipe is filled with a plurality of tubes or standpipes of different diameter. The tubes project out of the pipe into the internal volume of a funnel collector on the upper end of the pipe, and require the solution to pool in the funnel before entering the pipe. The tubes are positioned at different heights to regulate the flow within desired limits.

These and other novel features of the present invention will be apparent by reference to the accompanying drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a preferred closed cycle electrical power generation system especially adapted for a deep basing environment and using the hydrogen generator of the present invention.

FIG. 2 is a detailed schematic of the hydrogen generator shown in FIG. 1.

FIG. 3 is a detailed sectional view of one processing stage of the hydrogen generator of FIG. 2.

FIG. 4 is another detailed sectional view of a processing stage, similar to FIG. 3, showing a sliding tray within the retaining vessel.

FIG. 5 is yet another detailed sectional view, similar to FIGS. 3 and 4, showing the tray at a different height.

FIG. 6 is a schematic sectional detail of the collector and surge control, generally designated by the circle in FIG. 3.

FIG. 7 is a detailed sectional schematic of another preferred embodiment of the hydrogen generator of the present invention.

FIG. 8 is a detailed sectional view, similar to FIG. 3, showing a single processing stage of the generator of FIG. 7.

FIG. 9 is a detailed schematic of a preferred solid feed system for the generator of the present invention.

FIG. 10 is a detailed sectional view of a preferred embodiment of the hydrogen generator of the present invention.

BEST MODE CONTEMPLATED FOR CARRYING OUT THE INVENTION

1. The Nature of the Problem

Protecting strategic systems and personnel from nuclear weapon effects is becoming more difficult as weapon kill effectiveness improves. One attractive concept for such protection, known as deep basing, would locate the facilities several thousand feet underground. These deep basing environments, however, create unique problems associated with the close-cycle living environment that is necessary for survival. Essential to the survival and post-attack usefulness of such a base is a power source that can operate in this environment without access to outside resources, such as combustion air, sources of cooling, or large capacity waste disposal facilities, especially of hazardous wastes. The power system, particularly for electrical energy, must be readily packaged, be shock isolated, and, most important, be efficient. Storage of hazaraous materials (reactants, intermediates, or wastes) should be avoided. The system should be capable of laying dormant for extended time periods without degradation.

As described in a paper by William Harris entitled "Chlorine as an Oxidizer for a Closed Cycle Power Plant," delivered Feb. 13, 1985, a hydrogen-halide fuel cell is the best candidate for generating electricity for deep basing. Safe storage and handling of the reactants, hydrogen and halogen, however, is a primary concern to the implementation of a hydrogenhalide fuel cell. One feature of the present invention relates to a hydrogen generator that is capable of creating hydrogen on demand from by-products of the fuel cell, and that virtually eliminates the hazard of storing hydrogen gas.

Safety considerations dictate that large quantities of hydrogen gas cannot be stored in the deep basing environment. Hydrogen can be safely generated by the reaction of dilute hydrochloric acid (a by-product of the fuel cell operation) on a pure metal. Although a large selection of cations can be used as fuel for the hydrogen generator, selection of the fuel is dictated by several considerations. For example, the fuel should be plentiful, should be readily available in a form that is easily used, and should be inexpensive. The heat released during the exothermic reaction between the acid and the metal should be as low as possible to minimize heat sink requirements. Finally, the waste products created in the reaction should remain soluble in water to allow easy removal and storage. Based upon these conditions, iron is the preferred metal, because it is readily available in pellet form, has a low heat of reaction with hydrochloric acid, and is inexpensive. Zinc is preferred for secondary reaction beds (where the acid is diluted), since zinc has a reaction rate with hydrochloric acid of about 500 times greater than that of iron. Both zinc and iron chlorides are compatible for the waste product solution, even when mixed. Although iron and zinc are preferred, other metals may be used, such as lead or copper.

Hydrogen as a primary fuel is becoming increasingly attractive as fossil fuel supplies dwindle. Hydrogen has a very high thermal heating value of about 60,000 BTU's per pound compared to about 20,000 BTU's per pound for fossil fuels. Although hydrogen is one of the most plentiful elements, use of hydrogen as a fuel has progressed slowly because of storage and handling problems resulting from the extreme flammability of hydrogen over a wide range of air mixtures at ambient temperatures.

Power sources for underground installation would be extremely vulnerable if large amounts of hydrogen were stored. Catholytic oxidation of hydrogen in fuel cells using oxygen or halogen gases (chlorine or bromine) appears, however, to be an efficient and preferred method for obtaining electrical energy in closed cycle underground systems. The most efficient fuel cell power system for the underground installations is probably a hydrogen-chlorine fuel cell, under development by Hamilton Standard Electro-chem, Inc., a division of United Technologies Corp., which produces electricity and by-product HCl.

The present invention uses the by-product hydrochloric acid to recycle the hydrogen safely and easily, thereby alleviating any storage problem for hydrogen in the deep basing environment. The unit can be compactly designed to minimize the length of hydrogen lines and allow isolation of the entire system on a shock isolation platform, if desired.

2. The Power System

As shown in FIG. 1, the deep basing closed cycle power system includes a hydrogen-chlorine fuel cell 10 having a cooling water inlet 12 and outlet 14 for controlling the reaction of chlorine and hydrogen within the fuel cell 10. Chlorine 16 enters a distributor 18 through a check valve 20 from liquid storage and enters the fuel cell 10 through a feed line 22. Other lines 24 on the distributor 18 direct chlorine 16 to other cells (not shown) in the power system.

Hydrogen 26 enters the fuel cell 10 through a feed line 28 from an accumulator 30, which also distributes the hydrogen 26 to the other cells. Electricity and heat are generated in the fuel cell 10. A waste product comprising hydrochloric acid in water and unreacted chlorine enters a pump 32 through line 34, and is pumped into a receiver 36 for the separation of chlorine gas from the acid solution. The gaseous chlorine is recycled through the check valve 38 and return line 40 to the chlorine distributor 18. Chlorine 16 may, alternatively, be added to the receiver 36 through line 42 and check valve 44 to increase the concentration of the acid solution.

The dilute hydrochloric acid solution leaves the receiver through line 46 and flow regulator 48, and enters the first stage of the hydrogen generator 50, the details of which will be described. Essentially pure hydrogen gas, created in the hydrogen generator 50, is diverted through line 52 to the hydrogen accumulator 30 through a flow regulator 54. A solid fuel feed system 56 allows the addition of metal particles 58 to the several beds 66 of the hydrogen generator 50 without contaminating the controlled environment of the generator.

A waste stream 60 is withdrawn from the bottom of the hydrogen generator 50, and includes a solution of metal chlorides in water with a trace of hydrochloric acid. This waste stream 60 is stored in suitable storage facilities, such as within a raise of the base that was originally used to store water.

During transit conditions, if excess hydrochloric acid is generated in the fuel cell 10 during consumption of hydrogen, this excess acid solution raises the pressure within the receiver 36 and opens check valve 38 to allow chlorine to flow into the fuel cell distributor 18 through line 40, thereby maintaining the pressure within the receiver 36. The small amount of HCl which is removed. in the waste stream 60 is replenished to the system through line 62 in the receiver 36.

As shown in FIG. 10, the solid fuel feed system 56 includes one or more fuel distribution lines 64 which direct the solid fuel to the reaction beds 66 within the generator 50. For clarity, the distribution lines 64 have been truncated in FIGS. 1, 2, and 7, and have been deleted entirely in FIGS. 3, 4, and 5.

3. The Generator

A preferred hydrogen generator 50 is illustrated schematically in FIG. 2 where the reaction of hydrochloric acid with metal particles is carried out in six process stages by flowing the hydrochloric acid progessively through six beds 66. The top four beds in the vertical stack of the hydrogen generator 50 are illustrated with patched lines designating that these beds contain iron particles, while the beds of the lower two processing stages are designated by circles to indicate that these beds contain zinc. The depth of particles in each bed is controllable to control the residence time of acid within each bed, thereby controlling the heat and hydrogen gas that are created.

Each processing stage of the hydrogen generator 50 includes a centrally located downcomer 68 which delivers the hydrochloric acid solution 70 to the bottom of each bed where the solution 70 flows upwardly through the bed 66 to create hydrogen during contact with the metal. Emerging from the top of the bed, the solution passes into an annulus 72 (FIG. 3) to a collector funnel 74 that leads to the downcomer 68 for the next lower stage.

Cooling water 76 flows across the base of each stage to cool the acid solution to control the reaction rate further. The waste stream 60 accumulates in the bottom of the generator 50 and may be scrubbed prior to pumping to waste storage.

Each processing stage of the hydrogen generator will now be described in greater detail with reference to FIGS. 3, 4, and 5.

The downcomer 68 preferably has two sections which telescope together as illustrated by the straight section 78 and bell receiving section 80 in FIG. 3. The telescoping sections allow the length of downcomer 68 to be varied, as will be explained. The bell section 80 passes through the bed 66 and through a distributor plate 82 mounted within a sliding tray 84. The distributor plate 82 has a plurality of holes to allow the passage of the hydrochloric acid solution 70 upwardly through the distributor plate 82 and into the bed 66. The distributor plate 82 is positioned slightly above the bottom 86 of the sliding tray 84 to define a cavity 88 between the bottom 86 and the plate 82. The cavity allows uniform distribution of the acid solution across the bottom of the bed 66, which rests above the distributor plate. Thus, the hydrochloric acid solution flows countergravity through the bed 66 at a flow-rate and velocity slow enough to avoid fluidizing the particles of the bed so that (1) optimum reaction conditions are achieved, (2) the particles are completely dissolved, and (3) no particles are entrained in the solution or are carried from the bed. The maximum amount of hydrogen is created from the minimum amount of metal.

The sliding tray 84 is received within a retaining vessel 90 to create a fluid seal between the side of the tray 84 and the wall of the vessel 90. As illustrated in FIGS. 3, 4, and 5, the tray can move upwardly and downwardly in the vessel 90 between the bottom of the vessel 92 and an end-of-motion limit 94 on the open end of the vessel.

Cooling water 76 entering the retaining vessel 90 through a feed line 96 in the outer jacket 98 can be used to lift the sliding tray 84 by restricting flow of the water from the vessel with a back pressure valve 100 on the outlet 101. The cooling water 76 within the retaining vessel 90 defines a chamber 102 between the bottom of the tray 86 and the bottom of the vessel 92 that has a variable volume. When this chamber 102 is increased in volume (raising the sliding tray 84), a port 104 on the tray can register with a drain port 106 intermediate within the wall of the retaining vessel 90 so that the acid solution 70 does not enter the bed 66, but flows directly from the cavity 88 through the aligned ports 104 and 106 into the annulus 72 between the retaining vessel 90 and the outer jacket 98. Any fluid remaining in the bed also will drain hydrostatically back through the distributor plate 82 into the cavity 88 and out the aligned ports 104 and 106 into the annulus 72 so that the reaction may be quickly stopped.

One or more ports 108 near the top of the wall of the retaining vessel 90 above the top of the tray allow acid solution 70 that emerges from the bed 66 to drain into the annulus 72 without passing over the lip of the retaining vessel.

Fluid in the annulus 72 falls to a funnel collector 74 and pools there due to a surge control means which will be described. The collector 74 preferably includes a plurality of necked openings 112 to allow passage of gas 26 upwardly through the several stages of the generator 50.

The surge control means is more completely shown in FIG. 6 As illustrated there, the downcomer 68 is filled with a plurality of tubes or standpipes 114, 116, 118, and 120 having different diameters and being positioned at different heights above the base of the funnel collector 74 so that solution must pool on the collector 74 before it enters the downcomer 68. If a surge of solution were to enter the funnel collector 74 (as by raising the sliding tray of an upper stage to align the ports 104 and 106) the standpipes 114, 116, 118, and 120 prevent a surge of solution from reaching the next stage. The surge control means, having no moving parts, protects against inadvertent introduction of acid to the beds during transit conditions (start-up, shutdown, loading, etc). The downcomers 68 may also include a "go - no go" valve 122 having a first portion 124 to seal the downcomer 68 and a second portion having an opening 126 to allow unrestricted flow of solution through the downcomer 68. This valve allows complete shut-off of lower stages in the generator.

FIGS. 7 and 8 illustrate an alternative preferred embodiment of the present invention. Identical reference numbers are used to identify analagous parts between the embodiments. Again, the hydrogen generator 130 (FIG. 7) includes six beds 66 stacked within the reactor to generate hydrogen gas in successive stages. The upper beds 66 within the reactor usually are filled with pure iron particles while the lower beds contain zinc.

The differences in construction between the two embodiments is best understood with reference to FIG. 8. Each processing stage includes a base 132 that includes an internal channel 134 for the circulation of cooling water 76 from an inlet 96 to the outlet 101. The base 132 also includes a through-hole 138 on one side of the base to allow the passage of acid solution 70 downwardly through the base to the next processing stage and hydrogen gas 26 upwardly to the bonnet at the top of the generator 130.

The channel 134 has two segments within the base and a portion of variable volume defined by the base 132 and the bottom 86 of a sliding tray received between the walls 140 of a receiver or retainer vessel (generally being a 12 inch diameter teflonlined pipe) affixed to the base 132. A top plate or retaining ring 144 seats on the wall 140 and serves as a stop limit for movement of the sliding tray relative to the base 132 within the vessel.

A distributor plate 82 mounted within the sliding tray above the bottom 86 creates a cavity 88 into which the downcomer 68 (made of telescoping sections 78 and 80) delivers hydrochloric acid solution 70 for distribution upperwardly through the distributor plate 82 into the beds 66. The bell section 80 of the downcomer 68 may include an internal funnel 146 to further control flow of acid 70 to the cavity 88. The telescoping sections 78 and 80 allow the sliding tray to move relative to the base 132 and relative to the collector 74 of the next higher stage in the generator 130.

Drain ports 104 and 106 allow the rapid draining of the reactor bed by shunting fluid directly from the cavity 88 to the through-hole 138.

Pipe flanges 148 connect the base plates 132 to each section of the outer jacket 136 (formed from a 16 inch diameter TEFLON-lined pipe). As can be seen by comparison of FIGS. 3 and 8, the major difference between the two embodiments of the generator is that in one (FIG. 3) the retaining vessel is mounted within the outer jacket 98, while in the other (FIG. 8) the base 132 and jacket 136 together form the structure of the generator.

This embodiment allows the number of trays within the generator to be varied, since each processing stage is separable from the stack. Consequently, however, the possibility of leaks is increased, since there are a greater number of seals.

Drain ports 143 and 145 in both the tray 84 and vessel walls 140 are necessary in a second preferred embodiment to allow acid 70 to reach the passageway leading to the through-hole 138.

A water powered TEFLON shut-off valve 142 is positioned in the downcomer 68 to help control flow of acid between stages.

Referring to FIG. 9, the preferred solid fuel feed system will now be described.

The system 56 includes a receiving hopper 150 having an inlet (not shown) to allow introduction of metal particles 58 into the hopper 150 when the hopper is vented to the atmosphere. The hopper 150 is connected through vacuum line 152 to a vacuum pump 154, which may be used to evacuate the hopper 150 to a pressure of about 1 psia or less, after the introduction of the metal particles to the hopper. The vacuum line is also connected through a two position valve 156 to a reservoir 158 of an inert gas, such as nitrogen. Following evacuation of the hopper, the vacuum pump 154 is stopped, and the valve 156 is opened to allow a positive pressure of gas to enter the receiving hopper 150 from the reservoir 158. This gas should be relatively insoluble in water and should be essentially nonreactive with the metal particles. The gas is used in the hopper to prevent any damaging oxidation of the metal particles while they are stored in the hopper prior to injection into the hydrogen generator 50.

The receiving hopper 150 is connected to an injector 160 with one or more conduits 162 that allow metal particles within the receiving hopper 150 to be fed by gravity or otherwise to the injector 160. Each conduit 162 preferably includes two or more valves 164 which can be closed to isolate the injector 160 from the receiving hopper 150. These valves 164 are particularly important to alleviate hydrogen leakage between the injector and the receiving hopper.

The injector 160 is generally cylindrical, and includes a piston 166 that can reciprocate within the injector between the upper position shown in solid lines in FIG. 9 and a lower position schematically illustrated by the dotted lines 168 in FIG. 9. The movement of the piston 166 is achieved by injecting water 170 behind the piston 166 through a port 172 at the top of the injector 160 or an exhaust port 174 near the bottom of the injector. A control valve 176 in the water infeed line above the port 172 allows the flow of water to be controlled and allows fluid to be diverted from the injector through the port 172 to an exhaust line 178 to drain the injector when the piston moves from the lower position 168 to the upper position.

Similarly, a control valve 180 connected with the exhaust port 174 allows the water 170 to be shut off, and the injector 160 to communicate with a waste line 182 for draining.

An overflow drain 184, including a flow control valve 186 is connected to the injector 160 above the connecting conduits 162 to allow draining of water 170 from the injector when metal particles are transferred from the receiving hopper 150 to the injector 160. Entrained gas that is conveyed to the injector from the receiving hopper by the particles is of a lower density than the water within the injector, rises to the top of the injector, and is bled from the injector through the drain 184. The metal particles displace water within the injector and form a mixture of the metal particles and water only.

A valve 188 at the bottom of the injector 160 isolates the injector from the generator 50, and allows the injector to be filled with water 170 through line 174 prior to transfer of metal particles 58 from the receiving hopper 150 to the injector 160, as has been described. With metal particles in the injector, the control valves 164, 180, and 186 are closed, and hydrogen gas 26 passes from the generator 50 to the injector through line 190 by opening a control valve 192 in the line 190. The gas 26 enters the injector 160 near the upper end of the injector in the vicinity of the drain 184. With the valve 192 open, the control valve 180 is opened to allow the entering gas to drive the water between the particles in the injector out the waste line 182, leaving a combination of metal particles, hydrogen gas, and a small amount of entrained water within the injector. Then, the control valve 192 is closed and the valve 188 is opened. Water pressure is created behind piston 166 to drive the piston downwardly in the injector and to force metal particles, entrained gas, and water through fuel supply lines 64 into the generator 50. Distributor heads 194 rotate under the pressure of the metal particles in the supply lines 64 to distribute the particles uniformly over the bed 66.

A sight glass 196 on the side of the injector allows the operator to know the level of liquid in the injector 160 by viewing the meniscus between the liquid and gaseous phases.

While preferred embodiments of the invention have been shown and described, those skilled in the art will readily recognize alterations, modifications, or variations that might be made to the preferred embodiments without departing from the inventive concept. The description and drawings are meant to illustrate the invention and not to limit it. The claims should be interpreted liberally in light of the description and drawings to protect the invention as described in the preferred embodiments and their full range of equivalents. The claims should only be limited as is necessary in view of the pertinent prior art. 

We claim:
 1. A reactor, suitable for reacting an acid with at least one metal to form hydrogen gas, comprising:(a) an outer jacket; and (b) a first processing stage, including:(i) a retaining vessel mounted in the jacket and defining an annulus between the jacket and the vessel, the vessel including a bottom and an open end; (ii) a tray, having an open end and a bottom, received within the vessel through the vessel's open end to create a substantial fluid seal between the vessel and the tray, the vessel and tray defining a variable volume chamber between the bottom of the vessel and the bottom of the tray, the tray being positioned to slide within the vessel; (iii) a distributor plate mounted in the tray above the tray bottom to define a cavity between the plate and the tray bottom, the plate including a plurality of openings allowing circulation of fluid through the plate; (iv) a feed line through the jacket and in fluid communication with the cavity for supplying fluid to the cavity; (v) an inlet in the jacket and in fluid communication with the chamber for defining a channel allowing control fluid to enter the chamber; and (vi) an outlet in the jacket and in fluid communication with the chamber allowing control fluid to exit the chamber.
 2. The reactor of claim 1 further comprising a second processing stage mounted in the jacket below the first processing stage, the second processing stage including a second retaining vessel, a second sliding tray, a second distributor plate, a second outlet, the two processing stages being stacked within the jacket.
 3. The reactor of claim 2 further comprising a collector positioned and arranged between the first and second processing stages for collecting a reaction fluid from the annulus of the first processing stage and for directing the reaction fluid to a cavity within the second tray.
 4. The reactor of claim 3 wherein the collector includes at least one passageway allowing gas to flow upwardly in the jacket through the collector.
 5. The reactor of claim 3 further comprising surge control means positioned within the jacket for regulating the flow of the reaction fluid to the cavity.
 6. The reactor of claim 3 wherein the collector includes a telescoping conduit positioned and arranged to accommodate upward and downward motion of the tray of the second processing stage relative to the retaining vessel of the first processing stage.
 7. The reactor of claim 1 further comprising a plurality of metal particles on the distributor plate in the tray, the particles defining a reaction bed.
 8. The reactor of claim 1 wherein the tray has a drain port communicating with the cavity through the tray wall and being registerable with a corresponding port in the vessel for draining fluid in the cavity directly to the annulus.
 9. The reactor of claim 8 further comprising a stop positioned on the vessel for limiting motion of the tray upwardly toward the open end of the vessel.
 10. The reactor of claim 1 further comprising:(a) means for introducing solid metal particles to the tray to form a bed within the tray; (b) a product gas outlet in the jacket above the vessel; and (c) a waste fluid outlet in the jacket below the vessel.
 11. A reactor for holding reaction beds in stacked array, comprising:(a) an outer jacket; (b) a plurality of retaining vessels stacked within the jacket, each of said vessels having a bottom and an open end; (c) a plurality of trays, each of said trays having an open end and a bottom, one tray received within each of said vessels to create a substantially fluid seal between the tray and the vessel, each of said trays and vessels being positioned so as to define a variable volume chamber between the bottom of each of said vessels and the bottom of each of said trays, each of said trays being positioned to slide within the vessel in which the tray is received; (d) a plurality of distributor plates, one of said plates being mounted in each of said trays above the tray bottom to define a cavity between the plate and the tray bottom, each of said plates including a plurality of openings allowing circulation of fluid through each of said plates; (e) a reaction fluid feed line through the jacket into the open end of the uppermost of said trays and through the plate of the uppermost tray for supplying a reaction fluid to the cavity of the uppermost tray, the feed line including a telescoping conduit positioned and arranged to accommodate motion of the uppermost tray within its vessel and being in fluid communication with the cavity of the uppermost tray; (f) a collector positioned and arranged in the jacket between the uppermost tray and the next lower tray in the stack for directing reaction fluid from the uppermost tray to the cavity of the next lower tray, the collector including at least one passageway allowing gas to flow upwardly through the collector and the collector also including a telescoping conduit positioned and arranged to accommodate motion of the next lower tray; (g) a refrigerant inlet positioned and arranged in the jacket for the uppermost vessel in the jacket, the inlet being in fluid communication with the chamber between the uppermost tray and the uppermost vessel to define a channel for refrigerant to flow into the chamber; (h) a refrigerant outlet positioned and arranged for the chamber between the uppermost tray and uppermost vessel, the refrigerant outlet being in fluid communication with the chamber to define an exit port for refrigerant from the chamber between the uppermost tray and the uppermost vessel, the refrigerant outlet including flow restriction control means positioned and arranged for regulating the flow of refrigerant through the chamber between the uppermost tray and the uppermost vessel; (i) a product outlet positioned and arranged in the jacket above the uppermost vessel in fluid communication with the interior of the jacket; and (j) a waste outlet positioned and arranged in the jacket below the product outlet in fluid communication with the interior of the jacket.
 12. The reactor of claim 11 further comprising a bed of metal particles on the distribution plate of each of said trays.
 13. The reactor of claim 12 wherein the metal particles are selected from the group consisting of iron or zinc.
 14. The reactor of claim 11 further comprising:(a) a tray port positioned in the uppermost tray between the tray bottom and the plate and communicating with the cavity of the uppermost tray, and (b) a drain port positioned in the uppermost vessel above its bottom, the drain port arranged to allow fluid in the cavity of the uppermost tray to drain to the collector when the drain port is in registration with the tray port.
 15. The reactor of claim 14 further comprising at least one opening positioned in each of said vessels above the open end of the tray for each of said vessels and being above the drain port, so as to allow passage of fluid into the annulus.
 16. The reactor of claim 11 further comprising surge control means positioned and arranged with the collector for regulating the flow of fluid from the uppermost tray to the cavity of the next lower tray.
 17. The reactor of claim 16 wherein the surge control means includes a plurality of standpipes positioned in the collector.
 18. A reactor, comprising:(a) a first base defining a first reaction stage including a channel within the base for coolant and a through-hole permitting fluid to pass through the base; (b) an outer jacket sealingly affixed to the base, defining a closed volume around the base; (c) a receiver rigidly mounted on the base and defining a passageway between the jacket and receiver, the passageway being in fluid communication with the through-hole; (d) a tray slidably received within the receiver, the tray including an open end, a bottom, and a distributor plate above the bottom to define a cavity within the tray; (e) a telescoping downcomer within the jacket for introducing fluid to the tray, the downcomer extending through the distributor plate to communicate with the cavity; (f) a drain port in the tray in fluid communication with the cavity; (g) a corresponding drain port in a sidewall of the receiver above the base positioned to allow flow of fluid from the tray into the passageway when the tray moves upwardly in the receiver so that the drain ports of the tray and receiver register; (h) a bed of metal particles on the distributor plate of the tray, filling the tray to a predetermined height; (i) an overflow port in the tray above the height of the bed in fluid communication with the passageway so that fluid entering the bed through the distributor plate may exit the tray into the passageway after passing through the bed; (j) an opening in the sidewall of the receiver being registerable with the overflow port of the tray to direct fluid from the tray into the passageway; and (k) a funnel collector mounted in the jacket below the base and arranged to receive fluid exiting from the through-hole.
 19. The reactor of claim 18 further comprising a second reaction stage in the jacket, positioned below the base and the funnel collector to receive fluid from the funnel collector.
 20. The reactor of claim 19 wherein the funnel collector includes at least one opening positioned to allow a gas in the jacket to flow upwardly from the second reaction stage to the through-hole.
 21. The reactor of claim 18 further comprising means positioned and arranged for introducing metal particles to the bed.
 22. A reactor comprising:(a) a receiver including a bottom, a fluid inlet, and a fluid outlet; (b) a tray slidably positioned within the receiver above the bottom of the receiver to form a substantially fluid seal between the tray and receiver, the tray being slidable within the receiver to define a variable volume chamber, the tray including a tray bottom and a distributor plate mounted above the tray bottom to define a tray cavity; (c) means for introducing a reaction fluid to the tray cavity; (d) a drain port positioned and arranged in the tray in fluid communication with the tray cavity; (e) a receiver port positioned and arranged in the receiver above both the fluid inlet and the fluid outlet of the receiver,wherein the drain port and the receiver port are positioned so that when a control fluid is introduced to the chamber through the fluid inlet, the tray rises in the receiver, and so that the reaction fluid in the tray cavity can drain from the tray cavity when the drain port aligns with the receiver port.
 23. The reactor of claim 22 further comprising means associated with the receiver for cooling the reaction fluid.
 24. The reactor of claim 23 wherein the cooling means includes a channel in the bottom of the receiver allowing coolant to pass below the tray cavity.
 25. The reactor of claim 22 further comprising a motion stop associated with the receiver and positioned and arranged for limiting the upward motion of the tray relative to the receiver bottom.
 26. A reactor comprising:(a) a base including a cooling channel within the base for coolant and a through-hole permitting a reaction fluid to pass through the base; (b) a receiver mounted on the base, including a wall, and defining a volume separated from the through-hole of the base by the wall; (c) a tray slidably mounted within the receiver, the tray having a bottom and a sidewall; (d) means for introducing a control fluid into the receiver between the receiver and the tray bottom to raise the tray; (e) a tray outlet in the sidewall of the tray; and (f) a drain port positioned in the wall of the receiver allowing fluid communication between the tray and the through-hole when the drain port and tray outlet are aligned.
 27. The reactor of claim 26 further comprising a distributor plate mounted within the tray to define a tray cavity, and delete "and the outlet communicating with the cavity, the distributor plate including a plurality of openings allowing fluid circulation through the distributor plate.
 28. The reactor of claim 27 further comprising a bed of particles on the distributor plate in the tray.
 29. The reactor of claim 28 further comprising means for introducing a reaction fluid to the tray cavity. 